1. Field of the Invention
The present invention relates to a head amplifier for a head that magnetically writes and reads data signals, a recording and reproducing control circuit including the head amplifier, and a magnetic recording and reproducing apparatus including the recording and reproducing control circuit, and, in particular, to a head amplifier for a head including a heating element for adjusting the flying height of the head with respect to a magnetic recording medium.
2. Description of the Related Art
Thin-film magnetic heads included in magnetic disk apparatuses, which are typical magnetic recording and reproducing apparatuses, hydrodynamically fly above rotating magnetic disks with predetermined gaps (flying heights), while in writing and reading signals. A thin-film magnetic head, in this flying state, uses an electromagnetic coil element, which functions as a write head element, to apply a magnetic field to a magnetic disk to write a data signal, and uses a magnetoresistive effect (MR) element, which functions as a read head element, to sense a magnetic field from the magnetic disk to read a data signal.
The track widths of thin-film magnetic heads are significantly decreasing along with increasing recording densities of the magnetic disk apparatuses, which are increasing in capacity and decreasing in size in these years. In order to avoid reduction in writing and recording capabilities that can result from the decreased track widths, the flying heights of the recent magnetic disk apparatuses have been reduced. Actually, the flying heights are set to approximately 10 nm or less.
Such an ultra-low flying height must be stably controlled in order to prevent thermal asperities and crashes, thereby maintaining good write and read characteristics. As disclosed in U.S. Pat. No. 6,972,919B, JP2004-259323A, and US2006/0039077A, a technique has been developed and come to attention recently that provides a heating element in a thin-film magnetic head and uses heat from the heating element to protrude an end of the thin-film magnetic head toward the surface of a magnetic disk, thereby adjusting the flying height.
In order to heat the heating element provided in the thin-film magnetic head, a control circuit that controls heat generation of the heating element is required. As described in JP2004-259323A, the control function of the heating element has been implemented in a hard disk controller (HDC), which controls recording and reproducing.
With this configuration, a lead wire for applying a heat generating current to the heating element is required between the HDC and the magnetic head, in addition to signal lines for an electromagnetic coil element and an MR element provided between the HDC and the magnetic head via a head amplifier. These signal lines and lead wire are typically attached to a head gimbal assembly (HGA). JP2004-259323A discloses a technique that decreases the number of these signal lines and lead wires (transmission lines) to reduce the rigidity of the transmission lines so that nearly only the load set in the HGA itself is applied and the influence of the rigidity of the transmission lines on the flying control is reduced.
However, the conventional heat generation control method described above has a problem that the new function must be added to the HDC.
As has been described above, the HDC, used in a magnetic disk apparatus including a head that has a heating element for flying height adjustment, has the function of adjusting power supply to the heating element. FIG. 7 is a circuit block diagram showing a conventional control circuit of a magnetic recording and reproducing apparatus including a heating element for flying height adjustment. Referring to FIG. 7, an HDC 71 communicates data signals with an amplifier 700 for a write head element and an amplifier 701 for a read head element through a read and write (R/W) channel. Moreover the HDC 71 sends a control signal to a driver 702, which applies a heat generating current to a heating element, to control heat generation.
From this fact, it can be seen that an HDC that has been used in a magnetic disk apparatus including a head without a heating element cannot be used as the HDC 71 without modification. That is, there has been an inconvenience that, in the present state of the art, different HDCs need to be provided to control thin-film magnetic heads with and without heating elements.
Further, due to a distance between the HDC and the head amplifier, the heat generation delays, and possibly caused the difficulty of the timely flying height adjustment.